Polymerization reactors convert relatively low cost olefin monomers (e.g., ethylene, optionally in combination with one or more comonomers) into valuable polyolefin product (e.g., polyethylene).
It is well-known that the economics of polymer productions, including polyethylene production, strongly favor operating at a large scale and therefore, there has been a long standing desire to develop reactors of high capacity. However, the operation of large polymerization reactors, including tubular reactors, require special considerations. The reactors are generally operated at high pressure (e.g., 200 to 310 MPa) and high temperature (e.g., 150 to 450° C.). The polymerization reaction is highly exothermic. If the reaction mixture overheats, the olefins will decompose into carbon, hydrogen, and methane. Moreover, excessive temperature and/or pressure can present safety concerns. For these reasons, it is important to conduct the polymerization in a controlled manner and, if necessary, implement emergency shut-down of the reactor.
Emergency shut-down generally requires rapidly relieving the temperature and pressure conditions within the reactor by venting the reactor contents (e.g., a mixture of unreacted components and polymer particles) into the atmosphere. Separations systems, sometimes referred to as Emergency Vent Separators (“EVSs”), such as that disclosed in U.S. Patent Publication No. 2012/0275961, may be used to reduce the emission of polymer particles into the atmosphere during reactor shut-down.
Another EVS known in the art, designed by BASF, incorporates a vessel containing a liquid with multiple tangential inlets connected to various areas of a reactor. See, for example, U.S. Pat. Nos. 4,115,638 and 4,804,725. However, large reactors, including tubular reactors being manufactured today over 3.0 m3 volume or over 250 kta capacity present new problems related to the large mass flux of reactor effluent that must be rapidly vented from the reactor. EVSs such as that described above may not be well-suited to accommodate the massive forces and vibrations associated with such reactor size.
Other background references include EP 1 142 916 A.
An EVS for large reactors must sustain massive forces and vibrations while safely and cleanly managing large mass flux fluid flows of hot, potentially flammable reactor effluent during emergency shut-down. The demands placed on EVS equipment increase as the scale of operation is increased. Therefore, it would be desirable to have a system and method to safely and effectively separate particles from a high mass flux fluid flow during reactor shutdown.